Tungsten carbide dispersion in age-hardenable cupro-nickel

ABSTRACT

A SINTERED REFRACTORY METAL CARBIDE COMPOSITION IS PROVIDED COMPRISING ABOUT 35 V/O TO 70 V/O OF AT LEAST ONE REFRACTORY METAL CARBIDE SELECTED FROM THE GROUP CONSISTING OF WC, CBC, VC AND TAC DISPERSED SUBSTANTIALLY UNIFORMLY THROUGH A CUPRO-NICKEL MATRIX MAKING UP ESSENTIALLY THE BALANCE, THE CUPRO-NICKEL MATRIX CONSISTING ESSENTIALLY BY WEIGHT OF ABOUT 55% TO 90% COPPER AND THE BALANCE ESSENTIALLY ABOUT 45% TO 10% BY WEIGHT OF NICKEL. THE CUPRO-NICKEL ALLOY MATRIX IS PREFERABLY AGE-HARDENABLE. THE COMPOSITION IS PARTICULARLY ADAPTED TO THE MANUFACTURE OF NON-MAGNETIC WEAR AND CORROSION RESISTANT ELEMENTS FOR USE IN SALINE ENVIRONMENTS, SUCH AS A MATING RING IN ROTATING MECHANICAL SEAL APPLICATIONS IN TORPEDOES AND THE LIKE.

y 4, 1972 A. L. PRILL ET AL TUNGSTEN CARBIDE DISPERSION INAGE-HARDENABLE CUPRO-NICKEL Filed Oct. 21, 1970 FIG.

INVENTORS ARA/0L D L. PIP/L L STUART E. TARKAN 3,674,575 TUNGSTENCARBIDE DISPERSION IN AGE- HARDENABLE CUPRO-NICKEL Arnold L. Prill,Edmond, Okla., and Stuart E. Tarkan,

Munsey, N.Y., assignors to Chromalloy American Corporation, West Nyack,N.Y.

Filed Oct. 21, 1970, Ser. No. 82,769 Int. Cl. C22c 29/00, 31/04 US. Cl.148-325 14 Claims ABSTRACT OF THE DISCLQSURE A sintered refractory metalcarbide composition is provided comprising about 35 v/o to 70 v/o of atleast one refractory metal carbide selected from the group consisting ofWC, CbC, VC and TaC dispersed substantially uniformly through acupro-nickel matrix making up essentially the balance, the cupro-nickelmatrix consisting essentially by weight of about 55% to 90% copper andthe balance essentially about 45% to by weight of nickel. Thecupro-nickel alloy matrix is preferably age-hardenable. The compositionis particularly adapted to the manufacture of non-magnetic wear andcorrosion resistant elements for use in saline environments, such as amating ring in rotating mechanical seal applications in torpedoes andthe like.

This invention relates to a sintered refractory metal carbidecomposition and articles of manufacture thereof, such as shaft seals,which are characterized as being nonmagnetic and having improved wearand corrosion resistance in saline environments. The invention alsorelates to a method for producing such compositions.

Marine alloys are generally non-ferrous alloys containing copper as amajor alloying ingredient to provide resistance to corrosion in salineenvironments. An example of such alloys is cupro-nickel. However, suchalloys have their limitations in rotary seal applications due to lowresistance to wear. Attempts at improving wear resistance by addingstrengtheners, such as Ta, Cr, Al, Zr, etc., have not been verysatisfactory, the maximum hardness obtainable generally ranging up toabout 35 R Due to the inherent lack of wear resistance in typical marinealloys, manufacturers of marine equipment have made attempts at othersolutions to the problem, such as employing (1) a hard chrome plate, (2)flame or plasma spray coatings, and the like. The foregoing proposalshad certain inherent problems, such as spalling and chipping problemsdue to the lack of ductility of the coating relative to the more ductilesubstrate.

It thus became apparent that the solution to the problem would have toreside in providing a composition having the corrosion resistance ofmarine alloys but with markedly improved hardness without substantiallyadversely affecting the corrosion resistance.

It is thus the object of the invention to provide a hard, wear resistantand corrosion resistant composite alloy composition suitable for use insaline environments.

Another object is to provide, as an article of manufacture, anon-magnetic wear and corrosion resistant element, such as rotary shaftseals, having particular use in saline environments.

A still further object is to provide a wear resistant alloy compositioncharacterized by a high degree of inherent hardness and characterizedfurther by being further hardened through heat treatment.

The invention also provides as an object a powder metallurgy method forproducing hard wear resistant alloys suitable in marine applications.

These and other objects will more clearly appear when Patented July 4,1972 taken in conjunction with the following disclosure and theaccompanying drawing, wherein:

FIG. 1 depicts one embodiment of a mating ring for use in a mechanicalseal; and

FIG. 2 is illustrative of one use of the novel composition as a matingring seal for rotating shafts, especially where shafts are employed inmarine equipment, such as torpedoes.

Stating it broadly, the invention resides in a sintered compositionformed of at least one of the primary carbides WC, CbC, VC and TaC (e.g.about 35% to 70% by volume) dispersed substantially uniformly through amatrix of a cupro-nickel alloy making up the substantial balance, thematrix alloy consisting essentially by weight of about 55% to copper andthe balance essentially about 45% to 10% nickel. By primary carbide ismeant any one or more of the aforementioned carbides which is added tothe matrix as such, using powder metallurgy techniques of powderblending, of compressing the blended mixture into the desired shape andsintering the shape at an elevated sintering temperature, such as at themelting point of the matrix metal. The matrix metal may advantageouslycontain strengthening elements, such as age hardeners, for example, 0.5%to 3% by weight of alumi-I num.

Summarizing the foregoing, the refractory carbide may range from about35 v/o to 70 v/o or, more advantageously about 40 v/o to 60 v/o, and thebalance cupronickel matrix alloy ranging from about 30 We to 65 We andabout 40 We to 60 v/o, respectively. A particularly specific compositionis 45 v/o WC and 55 v/o matrix alloy.

As stated hereinabove, the composition of the matrix alloy may rangefrom about 55% to 90% by weight of copper and the balance essentiallyabout 45% to 10% nickel, the range more advantageously being by weightabout 60% to 75% copper and about 40% to 25% nickel, with or withoutabout 0.5% to 3% by weight aluminum as an age hardener, and 0 to about5% iron, more preferably 1 to 3% iron. A specific composition of thematrix metal by weight is 68.5% copper, 30% nickel and 1.5% aluminum.The alloy matrix may contain by Weight up to about 2% manganese and,more preferably, 0.5 to 1%.

As illustrative of the various embodiments of the invention, thefollowing examples are given:

EXAMPLE 1 An age hardenable wear and corrosion resistant composition wasproduced by dispersing 45 v/o WC through a matrix of 55 We ofcupro-nickel alloy containing by Weight about 68.5% copper, about 30nickel and 1.5 aluminum. In producing the carbidic composition, about60% by weight of WC powder is mixed with about 40% by weight of thealloying ingredients employed in producing the matrix metal as follows:

Grams WC (1 to 8 microns) 600 Cu (electrolytic, minus mesh) 274 Ni(carbonyl, 3 to 8 microns) .a 107 NiAl (minus 325 mesh) 19 The aluminumis added to the mixture in the form of nickel aluminide to avoid theloss thereof by evaporation during the early stages of high temperaturesintering.

To the 1000 gram mixture is added 1% by weight of paraffin wax and themixture ball milled for about 60 hours in a stainless steel ball millhalf filled with stainless steel b'alls using hexane as a vehicle. Aftermilling, the mixture is dried on a hot plate at 68 C. F.) until all thehexane is driven oif. The dry powder is then pressed into compacts orslugs at 15 tons per square inch. The compacts thus produced arepreferably subjected to liquid phase sintering in vacuum by heating themto about 1400 C. in vacuum for about 2 /2 hours and then held attemperature for about three-quarters of an hour, followed by cooling to1200 C., in 60 minutes and then furnace cooled from the foregoingtemperature to room temperature. The sintering is advantageously carriedout on a ceramic plate of previously fired Magnorite (a commercial MgOrefractory).

The sintered density of the sintered compact was about 99.3% oftheoretical and the compact exhibited an assintered hardness of about 51R and a solution annealed hardness of about 38 to 40 R when heated to1650 F. and held at temperature for about one hour followed by aircooling. Heating the quenched alloy at an age hardening temperature ofabout 932 F. for about 16 hours resulted in a hardness of 52 R Thesintered alloy in the annealed state is easy to machine to preciseshapes prior to age hardening and exhibits good resistance to seawatercorrosion. While the' metallographic structure is composite in nature,galvanic couples do not occur and, therefore, the alloy is not subjectto galvanic corrosion.

This alloy is excellent as seal material for rotary shafts in marineequipment. Other potential uses are non-sparking tools, weld wire guidesfor its good electrical conductivity and wear resistance.

EXAMPLE 2 Vol. percent Primary carbide About 55 Matrix metal About 45 1CbC.

The nominal composition of the matrix by weight is as follows:

Percent The foregoing composition is produced as in Example 1.

EXAMPLE 3 Vol. percent Primary carbide About 60 Matrix metal About 40The nominal composition of the matrix by weight is as follows:

Percent 100 EXAMPLE 4 Vol. percent Primary carbide -About 70 Matrixmetal About 30 The nominal composition of the matrix metal by weight isas follows:

Percent 4 EXAMPLE 5 Vol. percent Primary carbide -About 40 Matrix metalAbout 60 The nominal composition of the matrix metal by weight is asfollows:

The nominal composition of the matrix metal by weight is as follows:

Percent Cu 8 8 Ni 10 Fe l 1 A1 1 Broadly speaking, the sinteringtemperature may range from about 1050 C. to 1600 C., the time attemperature ranging from about 10 minutes to 4 hours. The sintering ispreferably carried out in vacuum. However, vacuum need not be employedso long as the pressed compact is sintered in a non-reactiveenvironment, such as in hydrogen, argon, etc.

Following sintering, the sintered body (where the matrix metal is agehardenable) is preferably solution annealed by heating to a temperaturein the range of about 750 C. (1382 F.) to 950 C. (1742 F.) for about 1to 4 hours, the annealed body thereafter cooled to room temperature,such as by agitated air cooling. The age hardening treatment consists ofheating the solution annealed body at a temperature of about 300 C. (572F.) to 700 C. (l292 F.) for about 1 to 25 hours and then air cooling.

The composite alloy produced in accordance with the invention ischaracterized in that it is machinable, is substantially non-magnetic,is particularly wear resistant and suitable for use in salineenvironments, such as seals for rotary shafts. A seal ring 10 is shownin FIG. 1, said seal ring having use as a mating ring in the mechanicalseal of FIG. 2. The mechanical seal of FIG. 2 is formed of an assemblyof an annular stainless steel cup 11, having confined in the cup-likeannulus thereof a graphite ring 12. The graphite ring has an annularright angled cutout 13 in which is confined an elastomer O-ring 14 formaintaining a positive seal between the seal ring and the cup. A matingring 10A is shown produced from the composite alloy of the invention inabutting relationship with the graphite seal and shaft 15, themechanical seal assembly being supported on shaft 15 as shown.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and the appended claims.

What is claimed is:

1. A sintered, machinable, non-magnetic, wear and corrosion resistantcarbidic composite alloy suitable for use in saline environments, saidalloy being formed of a sintered composition consisting essentially ofabout 35 v/o to 70 v/o of primary grains of at least one refractorycarbide selected from the group consisting of WC, CbC, VC and TaCdispersed substantially uniformly through a cupro-nickel matrix makingup essentially the balance, said cupro-nickel matrix consistingessentially by weight of about 55 w/o to 90 w/o copper, about 05%- to 3%aluminum, to about iron, 0 to 2% manganese and the balance essentiallyof about 45 w/o to w/o nickel, said cupro-nickel matrix being in theage-hardened condition.

2. The wear and corrosion resistant alloy of claim 1, wherein the amountof refractory carbide ranges from about 40 v/o to 60 v/o, and whereinthe cupro-nickel alloy matrix ranges from about 60 v/o to 40 v/o.

3. The wear and corrosion resistant alloy of claim 2, wherein therefractory carbide is tungsten carbide, and wherein the cupro-nickelmatrix alloy contains by weight about 55 w/o to 75 w/o copper and about45 w/o to 25 w/o nickel.

4. The wear and corrosion resistant alloy of claim 3, wherein the amountof tungsten carbide is approximately 45 w/o and the balance essentiallythe cupro-nickel alloy matrix containing approximately 1.5% by weight ofaluminum.

5. The wear and corrosion resistant alloy of claim 2, wherein therefractory carbide is columbium carbide.

6. The wear and corrosion resistant alloy of claim 2, wherein therefractory carbide is vanadium carbide.

7. The wear and corrosion resistant alloy of claim 2, wherein therefractory carbide is tantalum carbide.

8. As an article of manufacture, a machinable, nonmagnetic wear andcorrosion resistant element suitable for use in saline environments,said element being formed of a sintered composition consistingessentially of about 35 v/o to 70 v/o of primary grains of at least onerefractory carbide selected from the group consisting of WC, CbC, VC andTaC dispersed substantially uniformly through a cupro-nickel matrixmaking up essentially the balance, said cupro-nickel matrix consistingessentially by weight of about 55 w/o to 90 W/o of copper, about 0.5 to3% aluminum, 0 to 5% iron, 0 to 2% manganese and the balance essentiallyof about 45w/o to 10 w/o nickel, said cupro-nickel matrix being in theage-hardened condition.

9. The wear and corrosion resistant element of claim 8, wherein theamount of refractory carbide in the composition ranges from about 40 v/oto v/o, and wherein the cupro-nickel alloy matrix ranges from about 60v/o to 40 v/o.

10. The wear and corrosion resistant element of claim 9, wherein therefractory carbide is tungsten carbide, and wherein the cupro-nickelalloy matrix contains by weight about 55 w/o to w/o copper and about 45w/o to 25 W/o nickel.

11. The wear and corrosion resistant element of claim 10, wherein theamount of tungsten carbide in the composition is approximately 45 v/oand the balance essentially the cupro-nickel alloy matrix containingapproximately 1.5% by Weight of aluminum.

12. The wear and corrosion resistant element of claim 9, wherein therefractory carbide in the composition is columbium carbide.

13. The wear and corrosion resistant element of claim 9, wherein therefractory carbide in the composition is vanadium carbide.

14. The Wear and corrosion resistant element of claim 9, wherein therefractory carbide in the composition is tantalum carbide.

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